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Researchers Seek to Integrate THz Detectors and Electronics

Photonics.comOct 2006
BUFFALO, N.Y., Oct. 11, 2006 -- Sensors and detectors that work in the terahertz range show promise in applications ranging from precise identification of concealed weapons to the ability to distinguish between different tissue types for disease screening, but signals in that range are incompatible with conventional microelectronics. That situation might change, however, now that a group of researchers has been awarded a four-year, $1.2 million National Science Foundation (NFS) grant to develop semiconductor-based terahertz detectors that can be integrated with electronics.

University at Buffalo (UB) researchers and their collaborators at other institutions were awarded the grant under the NSF Nanoscale Interdisciplinary Research Teams (NIRT) initiative. In research being conducted by Andrea Markelz and Jonathan Bird of the University at Buffalo, the gray and yellow regions create a nanowire device that detects terahertz radiation emitted by a targeted substance.
Applications for the terahertz detectors are wide-ranging: from more secure signal-processing in telecommunications and precise imaging of real-time protein-binding in pharmaceutical research to more powerful homeland defense technologies.

"We are developing new types of sensitive, electromagnetic detectors that can be used at frequencies where no reliable technology currently exists," said Andrea Markelz, principal investigator and associate professor of physics in the UB College of Arts and Sciences.

These detectors, which could be integrated into large-scale arrays, would provide sophisticated signal processing capabilities, providing widely tunable response frequency, low power consumption and enhanced sensitivity. Among the devices the UB team will develop are those based on quantum dot arrays and hybrid devices. A quantum point contact terahertz detector likely will be furthest along in development at the end of the grant, Markelz said.

"The biggest advantage to this quantum point contact terahertz detector that we are developing is that it will provide spectral information, revealing many wavelengths at once, allowing for far more precise distinctions among similar objects," she said.

Such a powerful detector could assist potentially in detecting illegal or dangerous materials hidden in baggage or parcels; the terahertz range of the spectrum also is especially useful in detecting the binding of inhibitors with protein targets, allowing for rapid drug screening.

Markelz's expertise lies in characterizations of terahertz optical systems and materials at these frequencies, while co-principal investigator Jonathan Bird, professor of electrical engineering in the UB School of Engineering and Applied Sciences, focuses on fabrication and characterization of semiconductor nanodevices.

Bird, who studies the behavior of electrons in nanostructures, noted that the fundamental science of terahertz radiation will be enhanced by the research. "We will gain a detailed understanding of how the electrical properties of semiconductor nanodevices are modified in the presence of terahertz radiation," he said.

This NIRT collaboration especially is noteworthy because it provides an opportunity for experimental physicists and theoretical physicists, as well as electrical engineers, to tackle the same scientific problem.

"What is so wonderful about this grant is that the experimentalists will be able to say to the theorists, 'This is what we don't understand' and the theorists can then reconsider their models, based on what's happening with the real-world device," Markelz said.

The grant provides important avenues for outreach to underserved populations, since the theorists are based at Queens College and Kingsborough Community College, units of the City University of New York, which do not have graduate programs. The collaboration will provide state-of-the-art research opportunities to students at these institutions and encourage them to pursue higher degrees in science and engineering.

It also allows Markelz to continue GGems (Girls and Guys Exploring Math and Science), an educational program for high school students she launched with her NSF Career award that involves UB, the Buffalo Public Schools and the Buffalo Museum of Science, and aims to attract more females and other under-represented groups to the sciences. Other collaborators on the research are based at the University of California, Santa Barbara, the Institute of Physical and Chemical Research (RIKEN) in Japan and Sandia National Laboratories in Albuquerque, N.M.

Preliminary work on this research was funded through an Interdisciplinary Research and Creative Activities Fund (IRCAF) grant through the UB Office of the Vice President for Research. Related research by Markelz and Bird will be published soon in Applied Physics Letters.

1. A device designed to convert the energy of incident radiation into another form for the determination of the presence of the radiation. The device may function by electrical, photographic or visual means. 2. A device that provides an electric output that is a useful measure of the radiation that is incident on the device.